1. Field of the Invention
The invention relates to a technique, particularly apparatus and accompanying methods, for inclusion within, e.g., ISDN DTE, and use in conjunction with an ISDN terminal adapter for automatically, rapidly and transparently providing ISDN switch detection and SPID configuration, and which specifically and advantageously expedites ISDN configuration of DTE and decreases long-term support costs of the adapter.
2. Description of the Prior Art
In recent years, a number of domestic and foreign telephone companies have begun offering integrated service digital network (ISDN) services to their customers. ISDN provides an integrated voice and data network that offers both increased bandwidth and significant flexibility over traditional analog telephone services. Inasmuch as subscriber charges for ISDN access are decreasingxe2x80x94with the decrease being rather noticeable for some telephone companies, demand for ISDN service and equipment is rising appreciably. Demand is particularly strong and growing for those subscribers who seek cost-effective high speed access to the Internet.
In particular, a basic rate (BRIxe2x80x94so-called xe2x80x9c2B+Dxe2x80x9d service) ISDN interface provides higher speed bandwidth than both traditional analog, modem-based dial-up access modalities and comparably priced switched digital services. Each so-called B (xe2x80x9cbearerxe2x80x9d) channel, which carries subscriber voice and/or data, provides 64 Kbits/second of bandwidth; while a D (xe2x80x9cdataxe2x80x9d) channel, which carries signaling and control information, provides 16 Kbits/second of bandwidth. For the bandwidth delivered, an ISDN line is significantly less expensive than a private leased line that supplies the same bandwidth. Furthermore, ISDN, being a digital end-to-end service, provides digital transmission channels that tend to be more accurate and reliable, from the standpoint of error rates and dropped connections, than are conventional analog connections. In addition, ISDN service provides rapid connect times which, in turn, provide faster support for those LAN (local area network) protocols that require relatively short latency across WAN (wide area network) connections.
Starting a few years ago, various networking and communications equipment manufacturers have been offering relatively inexpensive ISDN terminal adapters for subscriber end-use. Such a terminal adapter, also generically referred to as xe2x80x9cdata circuit terminating equipmentxe2x80x9d (DCE), once connected to an ISDN connection and to a subscriber""s personal computer (PC), permits that subscriber to connect his(her) computer to, e.g., an Internet service provider and communicate at speeds approximately two to four times greater than a conventional analog modem. The computer so connected becomes so-called xe2x80x9cdata terminal equipmentxe2x80x9d (DTE). While the availability of these terminal adapters is clearly not the sole cause underlying the growth in ISDN usage, it, when combined with decreasing rates for ISDN service, is certainly a large and growing factor.
Ideally, an ISDN terminal adapter should be as easy for a subscriber to install and use as is a conventional analog modem. However, in practice, installing a conventional ISDN terminal adapter can be rather tedious, frustrating and time consuming. Many of these difficulties relate to a need for a user to manually supply the DTE, during its ISDN configuration, with a proper xe2x80x9cSPIDxe2x80x9d (service profile identifier) for each different ISDN directory number (for each different B-channel) that has been assigned to the DTE. In that regard and with most ISDN switches, each different DTE that is to be connected to an ISDN switch needs to be electronically identified to that switch by the SPID(s) assigned to it by a local telephone company. While a connection is being established between the DTE, via the DCE, and the switch, the DTE will send, to the switch and for each different B-channel it desires to use, an initialization message containing a SPID, entered by the user, for that particular channel. In response, the switch will establish a connection, with the DTE but only through the B-channel(s) that has a correct SPID. If the user configures the DTE with an incorrect SPID, then all attempts by the DTE to establish a connection, via the DCE, to the switch and over the B-channel associated with the incorrect SPID will invariably fail.
In particular, SPID formats unfortunately vary across the United States. Furthermore, given the length of a SPID, a subscriber often incorrectly enters a SPID into a terminal adapter during its configuration. Also, local telephone company personnel frequently, though inadvertently, supply a subscriber with an incorrect SPID that differs from that which has been programmed, for that subscriber, into a local ISDN switch.
As to varying SPID formats, for the most part, ISDN service is quite uniform across the entire United States and Canada; however, slight differences do exist as to how ISDN service is implemented among various local telephone companies. In particular, a small number of ISDN switch manufacturers currently exists which supply such switches to local telephone companies in the United States. These manufacturers currently include Northern Telecom, Ltd., Siemens Corporation and. Lucent Technologies, Inc. Northern Telecom and Siemens currently offer one ISDN switch each (carrying product designations xe2x80x9cDMS 100xe2x80x9d and xe2x80x9cEWSDxe2x80x9d, respectively)xe2x80x94each being a so-called xe2x80x9cNI-1xe2x80x9d type (referring to xe2x80x9cNational ISDN 1xe2x80x9d) switch and will be so referred to hereinafter. The Northern DMS 100 switch is available in two versions, i.e., an NI-1 version and a custom versionxe2x80x94those versions differing only in their software. Lucent Technologies (previously a portion of ATandT) currently offers three different ISDN switches (a xe2x80x9c5E Custom Multi-pointxe2x80x9d, xe2x80x9c5E NI-1xe2x80x9d and xe2x80x9c5E Custom Point-to-pointxe2x80x9d), though all implemented on a common 5ESS hardware platform (these switches differing in their generics, i.e., software). While these switches are generally compatible with each other, idiosyncratic differences, including differences in SPID format, do exist among the these switches. These differences complicate installation and use of an ISDN terminal adapter. A SPID in one format, hence suited for use with one type of ISDN switch, may not function with another type of ISDN switch; thus, completely preventing any ISDN calls from being established through the latter switch. Therefore, while configuring the adapter, a user must obtain SPIDs from his(her) local telephone company in the specific format for the local ISDN switch that will serve that user.
While configuring conventional ISDN terminal adapters for use with an ISDN line, an ISDN subscriber is usually required to manually enter SPIDs provided by his(her) telephone company for that line into the terminal adapter. Depending on the terminal adapter and the interconnected terminal equipment, the SPIDs may be programmed either into the adapter or the terminal equipment (DTE) itself. In any event, a significant probability exists that the subscriber will enter such a SPID incorrectly or that one of the SPID(s) (s)he receives will itself be incorrect. As to the latter, when an ISDN line is ordered from a local telephone company, then, to provision the service, SPIDs are established for that line and then generally entered manually, as data, by telephone company personnel into a database, accessible by the ISDN switch. The local telephone company then notifies the subscriber of his(her) SPIDs. However, given the length of a SPID and similarity of some of its digits, an individual at the telephone company can inadvertently transcribe a SPID incorrectly from that which was just assigned and thus provide the subscriber with an incorrect SPID.
Hence, it is the subscriber, during installing his(her) ISDN terminal adapter, who often experiences first-hand the effect of an incorrect SPID. Since the vast majority of subscribers have no knowledge of ISDN control messages, let alone the particular type of local ISDN switch to which (s)he is to connect and the corresponding SPID format required by that switch, many subscribers quickly discover that their ISDN terminal adapters will not function, for reasons that are not immediately apparent to or resolvable by them, and hence can become very frustrated and rather irritated. Such subscribers can and often do expend considerable time and effort in telephone conversations with customer service representatives of the local telephone company and/or their terminal adapter manufacturers in an effort to locate and cure the problemxe2x80x94a SPID error.
As a result, conventional ISDN terminal adapters have acquired a reputation, at least in the United States and Canada, as being quite time-consuming to install and properly configure. To complicate matters, the same difficulties arise if the subscriber merely moves the ISDN terminal adapter, which may have been programmed with a given SPID in one SPID format, to a different location, i.e., one served by a switch that requires a different SPID format.
Fortunately, the art teaches the concept, for use within an ISDN terminal adapter, of automatically detecting the type of ISDN switch to which the adapter is connected and then properly and automatically configuring the SPID for that switch. See, co-pending U.S. patent application to Reginald P. Best et al entitled xe2x80x9cApparatus for an Improved ISDN Terminal Adapter Having Automatic ISDN Switch Detection and Methods for Use Thereinxe2x80x9d Ser. No. 08/852,659, filed May 7, 1997 (hereinafter the xe2x80x9cBest ""659 applicationxe2x80x9d), which is assigned to the present assignee hereof and is incorporated by reference herein. In particular, the Best ""659 application describes an approach in which an ISDN terminal adapter analyzes particular D-channel ISDN initialization messages received from the switch as well as, where appropriate, responses, in terms of particular D-channel ISDN messages, received from the switch to specific ISDN messages sent by the adapter, and sets the switch type accordingly. The switch type value is then used, in conjunction with a directory telephone number of the subscriber, to access an internal database, specifically a table, of predefined SPID formats, referenced in terms of telephone area codes and switch types, to access the possible SPID format(s) for the ISDN switch to which the adapter is likely connected. To do so, a personal computer (PC), connected as DTE and interacting with the terminal adapter, forms one or more SPID(s) appropriate for both the type of ISDN switch to which the adapter is connected and the area code of the subscriber; queries the switch, through the adapter, with each of these SPIDs to select and verify a correct SPID from those formed; and, based on the results obtained, further refines and updates, if necessary, the detected switch type.
While the approach taught by the Best ""659 application is quite useful and advantageous in facilitating installation of an ISDN terminal adapter, it does possess several drawbacks.
First, this approach relies on a table of SPID formats indexed by area code. Unfortunately, as the demand for telephone numbers continues to escalate across the United States, area codes frequently change over time. Therefore, this places a burden on the manufacturer of the terminal adapter to constantly keep updating and disseminating a new version of the table each time an area code changes. Not only does this complicate manufacturer support of the adapter but also it significantly increases its long-term support cost.
Furthermore, this approach relies on detecting the switch type and thereafter separately configuring each SPID in sequence. The latter is accomplished by sending a D-channel ISDN initialization message from the terminal adapter, for just one SPID, followed by simply waiting for and then analyzing a response obtained from the switch, and if necessary, repeating this process, as needed with different initialization messages and SPID formats. Such an approach disadvantageously lengthens the time needed to detect the switch type and properly configure the SPIDs.
Therefore, a specific need exists in the art for a technique for use with an ISDN terminal adapter that not only automatically detects the type of ISDN switch to which the adapter is connected and properly configures its SPIDs for that switch, but also does so in a relatively short interval of time and with reduced long-term support costs. Advantageously, such a technique should further simplify and expedite installation and configuration of an ISDN terminal adapter, possibly increasing the demand for such adapters throughout a user community.
The present invention overcomes the deficiencies in the art and satisfies this need by providing a technique for inclusion within, e.g., ISDN DTE, and use in conjunction with, e.g., an ISDN terminal adapter (as DCE) which permits that DTE to automatically, rapidly and transparently detect a type of local ISDN switch to which the DCE is connected and then properly and automatically configure the SPIDs for use with that particular switch. Furthermore, my inventive technique reduces, with respect to conventional ISDN terminal adapters, long-term support costs that would be incurred by the manufacturer of the terminal adapter.
In accordance with my invention, the technique automatically detects the switch type by analyzing D-channel ISDN initialization messages received from the local ISDN switch as well as, where appropriate, responses, in terms of D-channel ISDN messages, received from the switch to specific ISDN messages sent by the adapter, and sets the switch type accordingly.
If the switch type is determined to be one that requires a SPID, then a SPID is formed using a predefined generic format, for each B-channel through which communication is being established, and-sent to the switch, using an NI-1 terminal initialization request (also referred to herein as a xe2x80x9cpreliminaryxe2x80x9d initialization request message), to invoke initialization. Given the predominance of NI-1 ISDN lines currently in use, the generic SPID is in NI-1 format. Currently, a vast majority of ISDN lines in use across North America either uses this particular format or will be transitioning to this format.
If, however, the local ISDN switch is, e.g., an NI-1 switch but the switch will not recognize the generic SPID format, i.e., a different format is being used with this switch, as evident by the switch rejecting the SPID(s) in the generic format (i.e., rejecting the preliminary initialization request message), then one or more separate initialization request messages are subsequently sent to the switch. Here, each message contains a SPID but in a different format. The formats used across all such separate messages are ordered such that a first such message contains a SPID format that is most popularly used with this switch type, a next such message contains a next most popular SPID format in use with this type switch, and so forth. Such messages with different SPID formats are sent until either the switch initializes with a SPID in one such format or all such formats are exhausted.
In particular, to undertake SPID configuration, the switch type is used to access a database containing SPID formats indexed by switch type and, for a given switch type, ranked in terms of their usage popularity, i.e., relative number of installed subscriber lines using a particular SPID format for that type switch. A resulting list of SPIDs in different formats, for the detected switch type, is then formed, for each B-channel for which communication is being established, with SPID(s) in the most widely used format for that type switch being first on the list, followed by SPIDs in the next most widely used format and so forth. Hence, if two B-channels, each with its own directory number, are being established, then the list will contain a pair of differing SPIDs (one for each B-channel) for each different SPID format. Once the list is formed, separate initialization messages containing the first pair of SPIDs in the list are sent to the local switch to invoke initialization. If initialization succeeds, these particular SPIDs are then subsequently used. Also, to eliminate a need to repeat switch detection and SPID configuration whenever communication is later re-established with the same local switch, the switch type and SPID values are written to a registry, associated with the operating system of the PC, for subsequent access and use. Alternatively, if initialization fails, then each SPID in each successive pair of SPIDs in the list is sent, in a corresponding initialization message, to the local switch, until a pair of SPIDs in a common SPID format is found, if any from amongst those in the list, that successfully initializes with the switch. If no such pair of SPIDs is found, then an appropriate error message is generated and the user is prompted to verify that (s)he entered a correct 10-digit directory number.
To expedite initialization and reduce subscriber wait time, my inventive technique fabricates an initialization message for each different SPID that is to be used by the adapter and, if two such messages are formed, sends the second message without regard as to whether the local switch has responded to the first message. The local switch will then simply send its response to each such message. This advantageously eliminates a need, existing in the art, to wait for a switch response to the first initialization message prior to sending the second initialization message.
Since the SPID format database is stored in terms of usage popularity, and not area code, the database does not need to be updated whenever an area code is changed by a local telephone company (telco), thus simplifying and reducing the cost associated with long-term support. Furthermore, a SPID format database indexed by switch type and, within each type, ranked by usage popularity, is shorter, and hence easier to implement, than an area code based database.
As a feature of my inventive technique, the SPID format database can. be stored in a data file separate from an executable file that implements switch type detection and SPID configuration. As such, in the event another SPID format sees use in the future, then that format merely needs to be appropriately added to the SPID format file, i.e., inserted into the database, in a location dictated by its switch type and its relative popularity with respect to other formats for that switch type. The executable files themselves do not need to be modified. Moreover, given the increasing deployment of National NI-1 ISDN service, particularly using the generic SPID format, by local telcos throughout the United States and Canada, it is quite possible that the SPID format file may not need to be updated at all; thereby, further reducing long-term support costs which are likely to be incurred by the manufacturer of the terminal adapter.